Unless otherwise indicated herein, the description in this section is not prior art to the claims in this application and is not admitted to be prior art by inclusion in this section.
There is proposed a technique that prints color patches and detects the printed color patches with a sensor to calibrate its image formation process, thus ensuring accurate color reproduction. There is proposed a facilitated technique of a color sensor calibration. The color sensor calibration is executed for reducing change in output due to a secular change of a light emitting portion and a light receiving portion, which constitute a color sensor, and due to a change in temperature in a peripheral area, and reducing an influence of a reduced sensor output due to a stain on the sensor surface. There is additionally proposed a technique that selectively lights light sources whose number is less than the number of colors to be detected, thus ensuring the reduced number of light emitting sources and light receiving sensors.